In a conventional art, for the aforementioned object, a magnetic member is disposed on a back surface of a bar code bonded to a commodity or a tag indicating a commodity price, quality, and the like to correspond to a sensing system in which magnetism is utilized, and an action of illegally taking away the commodity or the like is monitored and prevented.
However, the aforementioned constitution has problems that a label or a tag is easily separated from the commodity, existence of the magnetic member is easily recognized, the member is cut or destroyed and a function of a theft preventing tag cannot be fulfilled. Moreover, in some form of the commodity as an object, it is difficult to dispose a seal or a tag for security.